Assessment of antibacterial activity in TiO2@SiO2-modified graphitic carbon nitride nanomaterials

Abstract

Aims: The aim of this study was to evaluate the antibacterial properties of a TiO2-SiO2/g-C3N4 nanocomposite synthesised using sol-gel and thermal polymerisation methods. Methodology and results: Field-Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-ray (EDX) analyses were used to characterise the surface topology of the nanocomposite. The antibacterial efficacies of the synthesised TiO2-SiO2/g-C3N4 were assessed through agar well diffusion, disk diffusion, and broth macrodilution (minimum inhibitory concentration, MIC) assays. The test microorganisms included two bacterial species: Escherichia coli and Staphylococcus aureus. No visible zones of inhibition (ZOIs) were observed in either the agar well or disk diffusion assays, likely due to limited diffusion, poor solubility, and the short-lived nature of reactive oxygen species (ROS). However, MIC testing in liquid media revealed notable antibacterial activity, with MIC values of 0.25% for E. coli and 1.0% for S. aureus. This was further corroborated by SEM analysis, which revealed significant morphological damage in both bacterial species, underscoring the antibacterial potential of the TiO2-SiO2/g-C3N4 nanocomposite. Conclusion, significance and impact of study: Results suggest that TiO2-SiO2/g-C3N4 nanocomposite demonstrated effective antibacterial activity through ROS-mediated mechanisms, particularly under aqueous conditions that facilitate close contact with bacterial cells. These findings highlight its potential as a versatile agent for controlling bacterial contamination, especially in applications such as wastewater treatment, where moist environments enhance photocatalytic performance.